1. Background of the Invention
The present invention relates to a clamping system for detachably connecting two parts, such as is used for coupling a workpiece or tool carrier, for example in the form of a tool base holder, to a manipulator unit such as a spindle of a machine tool, or for coupling tool system modules to one another.
2. Discussion of the Background
In such clamping systems the objective is to clamp the parts to be connected reliably and firmly against one another, thus ensuring exact positional fixation of the parts to be connected relative to each other via close-fitting engagement between the faces of a hollow shank of the one part and of a holding portion of the other part. The tightening or clamping of the two parts to be connected against one another is achieved by the fact that the hollow shank is pulled into the holding portion against an undercut clamping shoulder formed in the hollow shank during application of clamping members of a clamping device. In the process a pressing force is developed between plane faces of the parts to be connected, so that the two parts clamped against one another are provided with exact axial and also radial positional fixation by the firm connection between the close-fitting faces.
In more recent times there has been increasing acceptance of the hollow-shank clamping system, in which the hollow shank has either cylindrical or tapered structure. In the joined-together condition of the two parts to be connected to each other, the clamping members used for clamping the parts against one another ensure not only that an adequate axial pressing force is developed but also that the hollow shank experiences a certain radial flaring, whereby the accuracy of fit between hollow shank and holding portion is additionally improved.
In conventional clamping systems according to the principle described hereinabove, the assembly and disassembly of the clamping device in the holding portion provided therefor represents a special problem,. however, since the clamping system must also absorb the reactions to the clamping force in addition to ensuring exact axial and radial positional fixation of the two parts to be connected.
From German Patent Application DE A 4220873, there is known a clamping system for detachably connecting two parts, which preferably are rotationally symmetric, of which one part has a preferably cylindrical or tapered hollow shank and the other part has a corresponding holding portion for holding the hollow shank in accurately fitting relationship. There is provided a clamping device which is disposed concentrically in the holding portion and which, in the joined-together condition of the two parts, extends into the hollow shank of the one part and is provided with at least two clamping members which can move in opposite directions as well as with an actuating device for driving the clamping members, by means of which device the clamping members can be synchronously moved into and out of engagement with an undercut clamping shoulder of the hollow shank, whereby a pressing force is generated between plane faces of the two parts to be connected.
This clamping system is based on the principle described hereinabove of clamping two parts to be connected by a clamping device having clamping members. In this clamping system the problem cited hereinabove is solved by exact positional fixation of the parts to be connected, in that a support member decoupled from the clamping members as regards assembly is fixed interlockingly in the holding portion. The positionally fixed support member brings about bracing of the clamping members and thus indirectly absorbs the reactions to the clamping force. The indirect absorption of the reaction via the support member as well as the fastening and positional fixation thereof can be achieved, however, only by additional fixing and fastening elements. Furthermore, special assembly attachments are generally necessary.
In another known clamping system, as is described, for example, in German Patent DE C2 3807140, a plurality of loosely disposed or at least not distinctly fixed clamping elements must be nested interlockingly in the holding portion. In this case an additional support member is indeed unnecessary, but the direct nesting of the clamping elements is associated with considerable assembly complexity, since the individually disposed clamping elements are not distinctly fixed in assembly position. Accordingly, the clamping elements must be moved into a special assembly/disassembly position during assembly/disassembly. Additional components and assembly attachments are necessary for this purpose also.
From German Utility Model DE U1 29518660 there is known a clamping system according to the preamble of the new claim 1.
A threaded sleeve, a clamping ring and a plurality of segmented bracing elements are necessary for fixation of the clamping-element halves in the tool spindle. The head parts of the clamping-element halves are therefore braced against the undercut clamping shoulder of the tool mandrel via a xe2x80x9cmechanismxe2x80x9d formed by the clamping ring and the bracing elements.
The object of the present invention is therefore to provide a clamping system for two parts to be connected, for example a tool system module and a machine tool spindle, which clamping system on the one hand performs adequately with a minimum of components and on the other hand permits simple, reliable and dimensionally stable coupling of the two parts to be connected without the need for additional assembly or fastening attachments.
This object is achieved by a clamping system with the features of claim 1.
According to the invention, the clamping elements are each provided in a region between head and foot portions with a retaining portion, which can be brought into engagement with an undercut recess of the holding portion.
Just as heretofore, therefore, the clamping members are still designed as head portions of elongated clamping elements disposed substantially parallel to the longitudinal or rotational axis of the holding portion. The clamping elements are constituents of the clamping device. The foot portions of the clamping elements are inventively connected to one another such that the clamping device has substantially the form of a V-shaped or U-shaped split chuck or clamping fork.
These clamping elements can be connected to one another movably, interlockingly and frictionally or in one piece. By means of an actuating device the clamping members can be made to move in opposite directions, or in other words to move toward or apart from one another. The inventive clamping system with such a predetermined arrangement of clamping elements relative to one another therefore obviates the support members which in conventional clamping systems are necessary for the clamping elements or clamping members.
This arrangement of the clamping elements also permits, without additional fixing components, distinct axial as well as radial fixation of the clamping members relative to one another in both the clamped position and detached position of the clamping system. The inventive clamping system is therefore characterized by simple and compact structure, which also permits reliable and dimensionally stable clamping of the parts to be connected without a plurality of loose components. In addition, the connection of the clamping elements in the manner described hereinabove creates a clamping device which, since it does not comprise any loose parts, can be fixed in the holding portion without great mechanical complexity.
Since, moreover, a minimum of movable parts is present in the inventive clamping system, only little friction is developed during movement thereof. In this way a relatively large clamping force is achieved between the two parts to be connected.
Further advantageous embodiments of the inventive clamping system are subject matter of the dependent claims.
The clamping elements are preferably designed as the arms of a U-shaped clamping fork of one-piece construction. In such a configuration the clamping device therefor e comprises only the clamping fork and the actuating device, and so the number of necessary components is reduced to two components. The one-piece configuration of the clamping elements in the form of a clamping fork further creates the possibility of increasing the clamping force between the two parts to be connected by bending stresses of the clamping fork. The clamping force is generated by the spring tension of the clamping fork when the actuating device is released. This spring tension can be adjusted by appropriate forming in the stress-free condition. The one-piece design of the clamping elements in the form of an elastically deformable clamping fork also permits simple assembly of the clamping device in the holding portion, since there is no need to dispose and fix a plurality of loose components.
It is also possible, however, to connect the clamping elements of the clamping device by an articulated joint which includes the foot portions of the clamping elements, the axis of rotation of which joint is disposed perpendicular to the longitudinal or rotational axis of the parts to be connected. This design provides substantially the same advantages as the one-piece design of the clamping elements.
The clamping device of the inventive clamping system is preferably provided in a region between head and foot portions with a radially outwardly projecting retaining portion in the form. of a clamping shoulder, and by means of this retaining portion can be nested in an undercut recess of the holding portion. By virtue of this technically simple expedient the clamping device can be engaged with or disengaged from the recess of the holding portion synchronously with the movement of the clamping members or with the pivoting movement of the clamping elements, depending on whether the clamping members are engaged with or disengaged from the undercut clamping shoulder of the hollow shank. Accordingly, therefore, axial fixation of the clamping device in the holding portion can be achieved without additional fixing elements.
In particular, the configuration of the recess in the form of a closed annular cross section does not represent any weakening of the nesting shoulder of the recess of the holding portion, as can occur in conventional clamping systems, for example due to countersunk portions in the case of a bayonet fastener. Compared with the production of a plurality of recesses, which extend in the direction of rotation of the tool holder only over portions of the inside circumferential wall of the holding portion, the production of a single recess in the form of a closed annular cross section additionally proves to be particularly simple. Such a configuration has also proved to be advantageous with regard to assembly of the clamping device, since the clamping device can be introduced: into the holding portion without any concern over its angular orientation relative to the holding portion.
In order to achieve the highest possible pressing force between the two parts to be connected, it has proved particularly advantageous to provide each of the clamping members with one wedge face, which cooperates with a mating wedge face provided on an undercut clamping shoulder of the hollow shank, this clamping shoulder preferably being formed by a recess in the form of a closed annular cross section. By means of this type of configuration, therefore, there can be created a wedge-type mechanism, which is characterized by relatively high efficiency.
According to a further development of the inventive clamping system, there is provided a push-off attachment which is automatically actuated or moved axially upon detachment of the engagement of the clamping members with the undercut clamping shoulder of the hollow shank. Axial actuation of the push-off attachment leads to separation of the two connected parts. In this case the forced movement of the clamping members upon detachment of the clamped engagement of the clamping members with the undercut shoulder can be utilized to generate a push-off force acting axially on the components to be separated.
According to the invention this is accomplished in simple manner by a push-off piston as part of the push-off attachment, which piston is disposed in a central recess of the part supporting the hollow shank and which, when the engagement of the clamping members with the undercut clamping shoulder of the hollow shank: is detached, can press synchronously with increasing force against a bracing face of the part supporting the hollow shank. By virtue of the central disposition of the push-off piston, therefore, a centrally acting, positive force is applied on the part supporting the hollow shank, ultimately leading to separation of the two connected parts. Because of the centrally acting force on the part supporting the hollow shank, the jamming and faulty gripping of the two parts that occur under some circumstances can also be prevented.
For this purpose it has proved advantageous to provide on the push-off piston a tapered face over which the clamping members can travel upon detachment of the clamping system. A sufficiently large push-off force between the parts can be generated with this simple xe2x80x9cwedge-type mechanismxe2x80x9d, and so even a firm connection produced by the fact that two parts with tapered close-fitting faces have been clamped together . . . with the detachment of the engagement of the clamping members with the undercut . . . .
When the push-off piston and the clamping device are held in sealed relationship in the corresponding recesses, preferably by sealing rings disposed in appropriate recesses, a coolant and lubricant can additionally be supplied via the parts clamped against one another to, for example, a cutting tool clamped in the one part. The seal of the push-off piston and of the clamping device can also be used to stabilize these components, and so vibration-induced chattering noise can be prevented.
Accordingly, the inventive clamping system can be combined with a coolant and lubricant supply system. This coolant and lubricant supply system comprises in particular a channel portion which is formed in the part supporting the holding portion, a channel portion which is formed in the part supporting the hollow shank, plus at least one line portion which bridges the clamping device and ensures fixation of its angular orientation. The line portion of the coolant and lubricant supply system can then ensure fixation of the angular orientation of the clamping device in the holding portion, and so further structural expedients or other fixation elements are not needed in this regard.
The line portion is preferably designed as a tube which is disposed between the parts to be connected, the end of this tube on the hollow-shaft side being held interlockingly and/or frictionally, preferably by sealed brazed joint, in a corresponding recess of the push-off piston, the shank portion of this tube being guided movably, preferably in a manner sealed by a sealing ring, through a corresponding recess in the connecting portion of the foot portions of the clamping elements, and the end of this tube on the holding-portion side being held in close-fitting relationship in a corresponding recess in the part supporting the holding portion.
As already described hereinabove, the line portion or the tube can be used for fixation of the angular orientation of the clamping device in the holding portion. The line portion or the tube is then disposed between the clamping members in such a way that the clamping members pinch the line portion or the tube between them when the clamping system is in detached position. This means that the coolant and lubricant supply system is securely retained in the holding portion without the need for additional fixation elements when the clamping system is in detached position.
Preferably the parts to be connected are designed as rotationally symmetric parts and the pressing faces of the parts to be connected are designed as radial annular faces. This contributes decisively to a simple and thus low-cost clamping system.
In order to achieve the most intimate possible connection between the two parts to be connected and thus to keep the torque-transfer losses as small as possible, the close-fitting faces between hollow shank and holding portion preferably have the form of tapered faces.
The drive of the actuation device is provided preferably via a radial opening oriented perpendicular to the longitudinal or rotational axis of the two parts to be connected, preferably via a radial bore, into which a tool, in the form, for example, of an Allen key, . . . from outside.
Furthermore, in a preferred embodiment of the clamping system, the actuating device for actuating the clamping members is constructed as a tightening screw with a head portion and a threaded portion, the head portion being disposed in a correspondingly configured recess of the one clamping member and the threaded portion in a corresponding threaded bore of the other clamping member.
An advantageous embodiment of the tightening screw has been found to be one in which the threaded portion of the tightening screw has a left-hand threaded portion and a right-hand threaded portion, of which one is disposed in the threaded bore of the other clamping member and the other is disposed in a nut functioning as the head portion, the nut being disposed in the correspondingly configured recess of the one clamping member. The advantage of this embodiment is that, by virtue of the left-hand/right-hand thread of the tightening screw, relatively small turning movements are necessary in order to bring about a relatively large xe2x80x9cstrokexe2x80x9d of the clamping elements; furthermore, the nut functioning as the head portion is subjected only to tension and thus does not undergo any frictional wear.
In addition to a rotationally symmetric configuration of the two parts to be connected, it has proved advantageous to make the clamping device also from a cylindrical part, so that the clamping elements and the clamping members have an arcuate outside face and the foot portion of the clamping elements has a cylindrical outside face.
As regards a simple possibility for limiting the clamping stroke of the clamping members, it has proved to be particularly advantageous when the clamping elements can bear against the inside circumferential wall of the recess of the holding portion while the two parts to be connected are in the tightened or clamped-together condition. In this way a maximum permissible clamping stroke of the clamping elements and thus of the clamping members can be safely maintained without additional limiting elements or stops.
In order to shorten the axial overall length of the clamping device and thus of the clamping system as a whole by a structurally simple means, it is further advantageous to provide each clamping element on the side of its foot portion with at least one notch which reduces the cross section. Thereby the force necessary to pinch the clamping elements together can be reduced and, as a positive consequence thereof, the necessary xe2x80x9clever-arm lengthxe2x80x9d of the clamping elements can be considerably shortened.
Further advantageous features of the present invention will become apparent from the description hereinafter, wherein a preferred practical example of this invention will be explained in more detail with reference to a schematic drawing.